lag problem? or something else?

[freally]

I'm making a program similar to the helicopter one, where you fly up and down and try to avoid the bricks...
its not done yet, (no collisions or boundaries) but i noticed when i was testing it out, the screen like flickers, i dunno if thats me, something wrong with my code, or just lag...

here is the code so far... its not very efficient, just starting to learn turing, so i don't know everything yet
no comment lines either

%race_car_game
var timed : real := 4
var distance : int := 0
var font1 : int
var x, y : int
var start : int := 0
var ready : string
var chars : array char of boolean
var box : int := maxx
var z : int := 0
var w : int := 0
var box2 : int
var box3 : int := maxx
var box4: int
x := 100
y := 100
var r:int:= 0
randint (box4, 100, maxy div 3 + maxy div 3 + 15)
randint (box2, 100, maxy div 3 + maxy div 3 + 15)
font1 := Font.New ("comicsans:10")
locate (1, 1)
put "Are You Ready?!? (yes/no)"
get ready
if ready = "yes" or ready = "Yes" or ready = "y" or ready = "Y" or ready = "YES" then
loop
timed := timed - 1
locate (1, 1)
put "Time: " ..
put timed
delay (1000)
exit when timed = 0
end loop
timed := 0
loop
cls
start := 1

r:= r + 5
if r > 220 and z < 630 then
drawfillbox (box - z, box2, box - 65 - z, box2 + 25, black)
z := z + 8
end if
if z >= 630 then
z := 0
randint (box2, 100, maxy div 3 + maxy div 3 + 15)
end if
if w < 630 then
drawfillbox (box3 - w, box4, box3 - 65 - w, box4 + 25, black)
w := w + 8
end if
if w >= 630 then
w := 0
randint (box4, 100, maxy div 3 + maxy div 3 + 15)
end if

drawfillbox (0, 35, maxx, maxy div 3 - 50, black)
drawfillbox (0, maxy div 3 + maxy div 3 + 50, maxx, maxy, black)


Input.KeyDown (chars)

if chars (KEY_UP_ARROW) then
y := y + 7
end if

if chars (KEY_DOWN_ARROW) then
y := y - 7
end if

drawfilloval (x, y, 15, 15, red)



if start = 1 then
timed := timed + .01
locate (24, 18)
put "Time: " ..
put timed
distance := distance + 1
locate (25, 18)
put "Distance: " ..
put distance
end if
drawfillbox (0, maxy div 2 + 5, maxx, maxy div 2 - 5, yellow)
delay (10)

end loop
end if

[gitoxa]

setscreen("offscreenonly")
View.Update

The two together will stop the program from drawing anything new on screen until it runs the "View.Update" line.
So you'll want to use that somewhere near the end of your loop.

the setscreen just goes at the top of your code.

[freally]

THANK YOU SOO MUCH!